1. Field of the Invention
The present invention relates to a vibrator and a vibratory gyroscope using the same, more particularly, it relates to the vibratory gyroscope used, for example, in a navigation system installed on a motor vehicle and the vibrator which may be used therein.
2. Description of the Prior Art
FIG. 50 is an illustrative view showing one example of a conventional vibratory gyroscope comprising a background of the present invention, FIG. 51 is a perspective view showing a vibrator of the vibratory gyroscope and FIG. 52 is a sectional view taken along the line LII--LII of FIG. 51. The vibrator 2 of the vibratory gyroscope 1 includes a quadrangular prism shaped vibrating body 3 of a constant elastic metal material or the like.
On a pair of opposing surfaces of the vibrating body 3, detecting piezoelectric elements 4, 4 are formed respectively. As shown in FIG. 52, the detecting piezoelectric element comprises electrodes 4b formed on both surfaces of a piezoelectric ceramic member 4a.
On a pair of side surfaces of the vibrating body 3 where the detecting piezoelectric element 4 is not formed, driving piezoelectric elements 5, 5 are formed respectively. The driving piezoelectric element 5 also comprises electrodes 5b on both surfaces of the piezoelectric ceramic member 5a similar to the detecting piezoelectric element 4. The vibratory gyroscope 1 is supported by supporting members 6, 6 extending through nodal points of the vibrating body 3.
A differential amplifier 7 is connected to the detecting piezoelectric element 4 of the vibrator 2, and an oscillator 8 is connected to the driving piezoelectric element 5. Thus, when the driving signal is supplied to the driving piezoelectric element 5, the vibrating body 3, as shown exaggeratively in FIG. 53, generates bending vibration in the direction perpendicular to the main surface of the driving piezoelectric element 5.
In such a state, if the vibratory gyroscope 1 is rotated, for example, about its axis, a Coriolis force is exerted in the direction perpendicular to the vibrating direction. Thus, as shown exaggeratively in FIG. 54, the vibrating direction of the vibrating body 3 is changed by the Coriolis force, and the output voltage is produced in the detecting piezoelectric element 4. Since the output voltage is proportional to a bending quantity in the direction perpendicular to the main surface of the detecting piezoelectric element 4, by measuring the output voltage, the rotational angular velocity of the vibratory gyroscope 1 can be determined. It is also the same even when the vibratory gyroscope 1 is rotated about any axis along its axis.
In such a conventional vibratory gyroscope, when the gyroscope is rotated, the bending direction of the vibrating body or the detecting piezoelectric element (a direction of a resultant vector of a bending vibration direction vector at non-rotation and a deviation vector by the Coriolis force) is in the direction deviating from the direction perpendicular to its main surface, so that the output voltage generated in the detecting piezoelectric element 5 was small. It was, therefore, difficult to measure the rotational angular velocity applied to the vibratory gyroscope from the output voltage. Accordingly, it was difficult to adjust the output voltage to zero, although required for determining the S/N ratio.